The trend to a higher integration and miniaturization of a semiconductor device has been accelerated from year to year.
For example, although a pattern with a line width of approximately 45 nm is nowadays formed by excimer exposure, formation of a pattern with a line width of 32 nm or less has been demanded recently along with further miniaturization of a semiconductor device. Conventional excimer exposure can hardly cope with such microfabrication. Therefore, change of exposure light to EUV (Extreme Ultra-Violet) light with a shorter wavelength has been studied.
EUV light has a property of being easily absorbed by any substance.
Therefore, in photolithography using EUV light as exposure light (hereinafter also referred to as “EUV lithography”), exposure is conducted using a catoptric system. Specifically, EUV light is reflected by an original plate corresponding to an exposure pattern, and a resist is exposed by the EUV light as reflected light. In this case, when a foreign substance is stuck to the original plate, EUV light is absorbed by the foreign substance or EUV light is scattered, as a result of which there are cases where a desired pattern is not formed by exposure.
Therefore, protection of an EUV light irradiation surface of an original plate with a pellicle has been studied.
A pellicle is configured to include a pellicle membrane for protecting an EUV light irradiation surface of an original plate, and a pellicle frame (support frame) supporting the pellicle membrane.
A pellicle membrane to be used for EUV lithography is required to have a high permeability with respect to EUV light, and to be resistant to degradation and deformation by EUV light irradiation. As a pellicle membrane satisfying the requirements, a silicon crystal membrane such as a single-crystal silicon membrane (for example, see documents 1 and 2), an aluminum nitride membrane layered on a metal mesh (for example, see document 3), a graphene membrane (for example, see document 4), and the like have been proposed.
Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2010-256434
Document 2: Japanese Patent Application Laid-Open (JP-A) No. 2009-116284
Document 3: Japanese Patent Application Laid-Open (JP-A) No. 2005-43895
Document 4: International Publication No. WO 2011/160861